System for controlling the setting of a quadruple band saw

ABSTRACT

A system for controlling the setting of a quadruple band saw having a fixed frame, a pair of rear and a pair of front sliding bases slidably mounted on the fixed frame and respectively supporting a pair of saw blades, and a drive unit for operating each pair of sliding bases in synchronism. The system comprises a first device for controlling the drive unit of the rear pair of sliding bases, and a second device for controlling the drive unit of the front pair of sliding bases to adjust the distance of the front pair of saw blades with respect to the rear pair of saw blades when the rear pair of saw blades is stationary and for maintaining a relative distance between the front and rear pairs of saw blades when the rear pair of saw blades is moving.

United States Patent Hedrei [541 SYSTEM-FOR CONTROLLING THE SETTING or AQUADRUPLE BAND [58] Field of Search ....143/5, 17, 22, 32 Q, 37, 37 B,143/115, 120, 120 A; 144/3 P; 83/20l.08, 201.09, 201.1, 201.11, 201.13

[56] References Cited UNITED STATES PATENTS 3,318,347 5/1967 Alich..143/22 3,086,568 4/ 1963 Hartzell ..143/ 120 A X 3,534,789 10/1970Morris ..143/37B [is] 3,703,196 51 Nov. 21, 1972 3,552,455 1/l9 71 Pinat..143/22 138,443 4/1873 Sillman.. 143/22 Primary Examiner-Andrew R.Juhasz Assistant Examiner-James F. Coan Attorney-Raymond A. Robic [5 7ABSTRACT A system for controlling the setting of a quadruple.

band saw having a fixed frame, a pair of rear and a pair of frontsliding bases slidably mounted on the I fixed frame and respectivelysupporting a pair of saw blades, and a drive unit for operating eachpair of sliding bases in synchronism. The system comprises a firstdevice for controlling the drive unit of the rear pair of sliding bases,and a second device for controlling the drive unit of the front pair ofsliding bases to adjust the distance of v the front pair of saw bladeswith respect to the rear pair of saw blades when the rear 9 Claims, 11Drawing Figures f6 /2 I? i l 30/ t I. 0 l o z 2 r s 52 ll I i a2 2 ii 2826 24 20 22 24 26 -2e 5 5a I 3 a 5 l I -1 P i o; m I 5 a i 5 5 i 1 4'PNENTEDNHVZI m2 3. 703; 19s SHEEI 1 0F 6 INVENTOR Constantin HEDREIATTORNEY PKTENTED 21 I97? 3. 7 03, l 98 SHEET 3 0F 6 IIIIIIIII I IINVENTOR Constantin HEDREI PATENTEDunm 1912 P7 L 0%;3 "oi rose-1r 1C/?8"2 R9 MI/IV CR1 0 up 2 L5 10 159 M10) 2 #10 I CRJISIII-NP9 INVENTORConstantin HEDREI A TTORNE Y PATENTEDNUY 21 I912 3 703; 19s

sum 8 0F 6 Consiuntin HEDREI ATTORNEY SYSTEM FOR CONTROLLING THE SETTINGOF A QUADRUPLE BAND SAW This invention relates to a system forcontrolling the setting of a quadruple band saw.

Quadruple band saws generally comprise a fixed frame, a pair of rear anda pair of front sliding bases slidable mounted on the fixed frame andrespectively supporting a pair of saw blades. Each pair of rear andfront sliding bases is moved transversely on the fixed frame by means ofa separate drive unit. Such quadruple band saws are very useful becausethey permit to cut three separate pieces of wood at a time in the samelog, namely a first piece using the rear pair of saw blades and twoother pieces, one on each side of such first piece using the front pairof saw blades.

In the known machines, the distances between the rear pair of saw bladesand between the front pair of saw blades are adjusted separately andthus, when the distance between the rear pair of saw blades is varied,it becomes necessary to readjust the distance between the front pair ofsaw blades. However, in a number of cases, the relative distance betweenthe rear and front pairs of saw blades which determines the thickness ofthe piece os wood sawed on either side of the first piece of wood doesnot vary. Such readjustment of the front pair of saw blades is thereforetime-consuming and consequently results in an increase in the price oflumber.

It is therefore the object of the present invention to provide a controlsystem for the setting of a quadruple band saw which permits to movesimultaneously the rear and front pairs of saw blades equal distancesfrom the center line of the quadruple band saw while maintaining apreset relative distance between the front and rear pairs of saw blades.The control systemalso permits to adjust the position of the front pairof saw blades with respect to the rear pair of saw blades.

. The control system, in accordance with the invention, comprises afirst device for controlling the drive unit of the rear pair of slidingbases and a second device for controlling the drive unit of the frontpair of sliding basses to adjust the distance of the front pair of sawblades with respect to the rear pair of saw blades when the rear pair ofsaw blades is stationary, and for maintaining a preset relative distancebetween the front pair of saw blades and the rear pair of saw bladeswhen the rear pair of saw blades is moving.

The first control device includes switching means located in theenergizing circuit of the rear drive unit and corresponding to thenumber of preset positions of the rear pair of saw blades, andpositioning means responsive to movement of the rear sliding bases adistance corresponding to a preset position for operating acorresponding one of the switching means to deenergize the rear driveunit.

The second control device includes switching means positioned in theenergizing circuit of the drive unit of the front pair of saw blades andcorresponding to the number of preset positions of the front pair of sawblades, and positioning means associated with the front sliding basesand responsive to the displacement of the front sliding bases when therear sliding bases are stationary for operating a switching meanscorresponding to a preset position of the front saw blades to denergizethe front drive unit when the preset position is reached.

The second control device further includes means responsive to themovement of the rear sliding bases under the control of the first deviceto energize the front drive unit to maintain a relative distance betweenthe rear and front pairs of saw blades.

The invention will be disclosed in more detail, by way of example, withreference to the description of a preferred embodiment thereof and tothe accompanying drawings in which FIG. 1 illustrates a schematic viewof the fixed frame, the sliding bases, the drive units and the controldevices of a quadruple band saw;

FIG. 2 illustrates a schematic view of the first device for controllingthe movement of the rear sliding bases;

FIGS. 3 and 4 illustrate the device for controlling the movement of thefront sliding bases while maintaining a relative distance between thefront and rear sliding bases when the rear sliding bases are moved underthe control of the first device;

FIGS. 5 and 6 illustrate the operation of the first and the secondcontrol devices;

FIGS. 7 and 8, when assembled as illustrated in FIG. 9, illustrate thecircuit diagram for controlling the drive units;

FIG. 10 illustrate a perspective view, with the cover removed, of a cambox used in the invention; and

FIG. 11 illustrates a section view through line 1 11 1 of the cam box ofFIG. 10.

Referring to FIG. 1, there is shown a quadruple band saw including afixed frame 10 upon which are mounted a rear pair of sliding bases 12and a front pair of sliding bases 14. The rear sliding bases 12 aremoved in synchronism towards or away from each other by means of aconventional drive unit 16. Similarly, the front sliding bases 14 aremoved in synchronism towards or away from each other by means of aseparate drive unit 18 identical to drive unit 16. Drive units 16 and 18comprise a motor M1 and M2 respectively driving a gear box 20 having twothreaded output shafts 22 coupled to nuts 24 secured to the slidingbases. The two shafts of gear box 20 rotate at the same speed and thethreads thereof are arranged to move the sliding bases in synchronismtowards or away from each other.

To each rear and front sliding bases is rotatably attached a pair oflarge wheels 26 holding a saw blade 28 in a known manner. The wheels 26are positioned on the sliding bases 12 so that the blades of each pairof saw blades are equally spaced from the center line of the quadrupleband saw.

The control device of the drive units consists of a first deviceindicated generally in FIG. 1 by reference numeral 30 and a seconddevice indicated generally by reference. numeral 32. Generally speaking,the first device 30 controls the drive unit of the rear pair of slidingbases. The second device 32 controls the drive unit of the front pair ofsliding bases to vary the distance of the front saw blades with respectto the rear saw blades when the rear saw blades are stationary.Furthermore, the second device is arranged to maintain a preset relativesetting distance between the front and rear saw blades when both pairsof saw blades are moved under the control of the first device 30.

The control device 30 is illustrated in detail in FIG. 2 and includes afirst bracket 34 secured to sliding base 12, a second bracket 36 securedto fixed frame and upon which is freely mounted a chain sprocket 38, anda cam box 40 having a chain sprocket 42 fixed at the end of its shaft. Achain 44 passes around chain sprockets 38 and 42 and has one end thereofsecured to sliding base 12 and the other end to first bracket 34. Itwill be clearly seen that movement of the sliding bases in the directionof arrow 46 will cause rotation of the shaft of the cam box 40 in thedirection of arrow 48 and vice versa. The operation of the controldevice will be disclosed more fully in a later part of the descriptionbut it may be worthwhile to mention now that cam box 40 contains anumber of cams which operate limit switches located in the energizingcircuit of drive unit 16, the number of cams in the cam box 40correspond ing to the number of preset positions of the rear pair of sawblades. The control device 30 thus acts as a positioning means formonitoring the displacement of the sliding bases 12 driven by drive unit16 and for stopping such sliding bases at a distance from the centerline of the quadruple band saw corresponding to a preset positiondetermined by the angular position of the cams on the shaft of the cambox 40.

Of course, other positioning means could be envisaged and suchpositioning means could include other means that chain 44 to monitor thedisplacement of the sliding base, and other means than a cam box forpositioning the sliding base at a preset location.

The control device 32 illustrated generally in FIG. 1 is shown in moredetail in FIGS. 3 and 4 of the drawings. It comprises a first bracket 50fixed to frame 10 at the front saw side and a'second bracket 52 fixed toframe 10 at the rear saw side. A shaft 53 is journalled in brackets 50and 52 and carries a chain sprocket 54 keyed at the front end thereofand a chain sprocket 56 keyed at the back end thereof. A chain sprocket58 is mounted freely on bracket 50 and a chain 60 passes around chainsprockets 54 and 58 and both ends of such chain are secured to slidingbase 14. It will be easily seen that displacement of the sliding base 14in the direction of arrow 62 will cause the rotation of shaft 52 in thedirection of arrow 64 and vice versa.

At the rear end of shaft 52, a chain 66 interconnects chain sprocket 56with four other chain sprockets 68, 70, 72 and 74. Chain sprocket 68 isfreely mounted on bracket 52; chain sprocket 70 is freely mounted on abracket 76 secured to sliding base 12; chain sprocket 72 is keyed on theend of the shaft of a cam box 78 mounted on the end of sliding base 12;finally chain sprocket 74 is freely mounted on a bracket 80 having means82 for tightening chain 66 around the various chain sprockets. Chainsprockets 68 and 70 are used to compensate for the variations in thedistance between shaft 53 and the shaft of the cam box 78 when the rearsliding bases are moved.

The cam box 78 controls the energization of the drive unit 18 associatedwith the front saw blades and contains a number of limit switches forthe purpose of positioning the front saw blades with respect to the rearsaw blades. Because cam box 78 is secured to the rear sliding bases itwill be seen that any displacement of the rear sliding bases willautomatically displace the cams of the cam box 78 and so causeenergization of the front drive unit to follow, with a slight delay, theenergization of the rear drive unit. It will also be easily seen that,when shaft 52 is rotated in the direction of arrow 64 by thedisplacement of the front sliding bases 14, as mentioned previously,chain 66 will be moved in the direction of arrow 86 to rotate the shaftof the cam box until a predetermined cam operates a predetermined limitswitch toopen the energization of the drive unit 18.

It will be easily understood that other positioning means could beenvisaged in place of device 32 and that such positioning means couldinclude other means that chain for monitoring the displacement of thefront sliding bases 14 and other means that a cam box for positioningthe sliding bases 14 at a preset location.

It is also to be understood that the firstdevice 30 does not necessarilyhave to be positioned on the right hand rear side of the quadruple bandsaw but could also positioned on the left hand rear side of the sawprovided that the second positioning device 32 is positioned on theright hand side of the saw.

The operation of the control devices of FIGS. 2 to 4 will now bedisclosed with additional reference to FIGS. 5 and 6 of the drawings.When both pairs of saw blades are moving simultaneously (FIG. 5) underthe control of the first and second devices 30 and 32, the shaft 53 ofthe second device 32 will be rotated by the movement of front slidingbases 14 and chain 66 will move in the direction of arrow 86, forexample (or in the opposite direction). However when the front slidingbases have moved, in the direction of arrow 62, a distance correspondingto the distance travelled by the rear sliding bases in the direction ofarrow 88, the cams of cam box 78 will return to their original positionbefore energization of the rear drive unit. Consequently, the frontdrive unit will be stopped. The relative setting distance x between thefront and rear saw blades will therefore remain constant as illustratedin FIG. 5.

When it is desired to vary the distance of the front saw blades withrespect to the rear saw blades, the front drive unit 18 is actuated andthe rear sliding bases remain stationary as illustrated in FIG. 6. Sincecam box 78 secured to rear sliding bases 12 does not move, chain 66 willrotate the shaft of the cam box 78 a predetermined distance y until thelimit switches are operated by the preset cam of the cam box 78.

The circuit diagram for controlling the drive units 16 and 18 isillustrated in FIGS. 7 and 9, when assembled as illustrated in FIG. 9.Referring to FIG. 7, the control voltage is derived from a transformerT, the primary of which is connected across two phases of a-three-phasesupply through fusible elements FUl and FU2. The secondary oftransformer T is applied to line L1 and L2 through manual switch SW andfuse FU3. Closure of manual switch SW operates pilot light P whichindicates that the circuit is ready for operation.

The rear drive unit 16 is powered by a three-phase motor Ml which isconnected to the three-phase supply through normally open contacts andM,IN-1 or M,OUT-1 depending on the desired direction of rotation of themotor. The motor is protected against overload currents by heaterelements 0L4 and 0L5.

The motor M1 is equipped with a magnetic brake which is energizedthrough a power supply including a fusible element FU6, a resistor RBI,and a bridge circuit including two capacitors C1 and C2 and two diodesD1 and D2 forming a rectifier and voltage doubler in a known manner. Theoutput of the bridge is applied to the winding PBl of the brake throughnormally closed contacts R9-1 and R-1 of relays R9 and R10 to bedisclosed later and through two variable resistance devices B1 and B2the resistance of which increases with the current flowing therethroughso as to apply a voltage to the winding of the brake which decreasesgradually after energization of the control unit. A capacitor C3 isconnected across the winding FBI to counteract the counter electromotiveforce generated by winding PBl. Let us mention at this stage thatcontacts R9-l and R10-1 control the release of the winding FBI and thatrelays R9 and R10 operating such contacts are energized at the same timeas the motor M 1.

Referring to FIG. 8, the secondary of transformer T is also applied tolines L3 and L4 through fuse FU7. The front drive unit is powered by athree-phase motor M2 which is connected to the three-phase supplythrough normally open contacts M lN-l or M OUT-1 depending on thedesired direction of rotation of motor M2. The motor M2 is protectedagainst overload currents by heater elements 0L8 and 0L9.

The front motor M2 is also equipped with a magnetic brake which isenergized through a power supply including a fusible element FU10, aresistor RE2 and a bridge circuit including two capacitors C4 and C5 andtwo diodes D4 and D5 forming a rectifier and voltage doubler in a knownmanner. The output of the bridge is applied to the winding PB2 of thebrake through normally closed contacts R-l and Rl6-l of relays R15 andR16 to be disclosed later and through two variable resistance devices B3and B4 the resistance of which increases with the current flowingtherethrough so as to apply an initial high voltage to the brake, whichvoltage will be reduced afterwards due to the increasing voltage dropagainst devices B3 and B4. A capacitor C6 is connected across windingPB2 to counteract the counter-electromotive force generated by windingPB2. As it will be easily understood contacts R15-l and R16-1 controlthe release of the brake and are operated at the same time as motor M2driving the front unit.

The control circuit illustrated in FIG. 7 is for an eight positionsetwork and therefore includes eight push buttons referred to as P081 toPOS8. Each push button except the first and the last one have onenormally open contacts (POS2-1) and two normally closed contacts (POS2 2and POS2-3). The first push button has a normally open contact POSl-land a single normally closed contact POSl-2. The last push button has anormally open contact POS8-1 and a single normally closed contactPOSS-3. The push buttons POSl to ing of contact POS7-3 willautomatically release any selection relay associated with positions P081to PO86. Similarly, the opening of contact POS7-2 will automaticallyrelease relay R8 if such relay has been previously operated. It will beclearly seen that the operation of any of the push buttons P081 to POS8will operate the corresponding relays R1 and R8 and that such relayswill lock operated through their own contacts Rl-l to R8-1. It will alsobe understood that the operation of any of the push buttons POSl to POSSwill open the normally closed contacts associated therewith toautomatically cancel any previous settings of the saw blades. Finally,pilots lights P1 to P8 are connected across relays R1 to R8 to indicatethe positions selected.

Relays CR,IN, CR OUT, CR1 to CR8 as well as limit switches LS1 to LS8are used in memory circuits which determine the direction of movement ofthe motor M1 driving the rear sliding bases of the quadruple band sawand also ensure the stopping of the motor at the selected position. Whenthe rear sliding bases are moving from one position to the other, thelimit switches LS1 to LS8 are operated by the cams of cam box 40 at eachposition but are released immediately after. The position of limitswitches LS1 to LS8 illustrated in FIG. 7 corresponds to the released.position of the limit switches. For example, when the rear slidingbases leave position POSl, representing the minimum setting POSS areassociated with the operation of a group of relays which control theselection of the various positions of the saw blades. The operation ofpush button POSl, for example, will energize relay R1 through normallyclosed contacts R17-1 or relay R17 to be disclosed later and through thenormally closed contacts POS2-3 to POSS-3. Relay R1 locks itselfoperated through its own contact Rl-l. The opening of the normallyclosed contact POS1-2 of push button POSl will release any other relayassociated with any other previous settings of the saw blades.Similarly, the operation of push button PO87 will operate relay R7 whichwill lock operated through its own contact R7-1. The openof the sawblades, towards a higher setting, limit switch LS1 is released and whenthe sliding bases reach position PO82, limit switch LS2 is operated. Theoperation of limit switch LS2 operates relay CR1 which lock operated onits own contact CR1-1 through the then released limit switch LS1.Similarly, when the sliding bases leave position POS2, limit switch LS2is released and when the sliding bases reach position POS3, limit switchLS3 is operated. The same operation will be repeated upon movement ofthe rear sliding bases towards higher positions POS4 to POS8, thusoperating relays CR3 to CR6.

It will be noted that the relays CR1 to CR6, when operated by thepassage of the sliding bases, remain operated and therefore maintaincontacts CR1-2 to CR6-2 closed and contacts CR1-3 to CR6-3 open. Thestate of the above mentioned contacts CR1-2 to CR6-2 and CR1-3 to CR6-3determines the direction that the sliding bases will take, that is thedirection of rotation of the motor Ml driving the sliding bases asfollows:

Let us assume that the sliding bases are in position POSl and that it isdesired to move them to position PO53. The operation of push button POS3will energize relay R3 which will lock operated through its own contactR3-l and also operate contact R3-2. The closure of contact R3-2 willenergize relay CR,OUT through normally closed contacts CR2-3 and CR,IN-l of released relays CR2 and CR IN. Relay CR OUT will close contactCR OUT-2 to energize relay M OUT and relay R10. The energization ofrelay R10 will release the brake as mentioned previously and theenergization of relay M OUT will operate contact M oUT-l to cause themotor M to rotate in the direction to move the sliding bases out towardsposition POS3. When the sliding bases reach position PO83, thecorresponding cam of the cam box 40 will operate limit switch LS3 todeenergize relay CR OUT which, in turn, will release relays R10 and MOUT.

Let us assume now that it is desired to return the sliding bases toposition PO82. Of course, I push button P082 will be operated and relayR2 will be energized closing contact R2-1 to lock itself operated andcontact R2-2. The previous movement of the sliding bases toward positionP083 has operated relays CR1 and CR2 to close contacts CR1-2 and CR2-2and open contacts CR1-3 and CR2-3. The opening of contact CR1-3 combinedwith the closure of contact CR1-2 thus complete a circuit for energizingrelay CRJN instead of relay CR OUT. The energization of relay CR lN willclose contact CR IN-2 in the circuit of relays R9 and M IN. Theenergization of relay R9 will open contact M9-l to release the magneticbrake of the motor M1. The energization of relay M IN will close contactM lN-l to operate motor M1 in the opposite direction to move the slidingbases in.

It will therefore be understood from the above that relays CR1 to CR6act as memory elements and determine the direction of rotation of themotor M1 and therefore the direction of movement of the sliding bases.Of course, the circuits associated with positions P081 and P088 do notrequire a memory circuit since they represent the limit positions of thesliding bases and may be reached from one direction only.

The limit switch LS1 is used to stop the sliding bases at position PO81when selected. In addition, limit switch LS1 is also used as a safetyswitch at the minimum setting position of the quadruple band saw. Limitswitch LS9 is used as a safety switch in the circuit of relay M UT forstopping the motor M1 at the maximum setting position. In addition, twoadditional limit switches LS and L811 are used on the fixed frame of thequadruple band saw to deenergize relays M lN and M OUT respectively uponfailure of the other limit switches.

Pilot light P9 is connected in series with normally closed contacts CRIN-3 and CR OUT-3 to indicate that the sliding bases have reached theirselected position.

It will also be noted that an overload device 0L is connected in serieswith relays M lN and M OUT for protecting the motor M against overload.

The control circuit of the front motor M2 as illustrated in FIG. 8 isfor a four position setwork. The positioning of the sliding bases drivenby motor M2 of the front drive unit is effected by means of four pushbuttons P0810 to P0813. Each push button except the first and the lastone have a normally open contact (P0811-1) and two normally closedcontacts (P0811- 2 and P0811-3). The first push button has a normallyopen contact P0810-1 and a single normally closed contact PO810-2,whereas the last push button P0813 has a normally open contact POSl3-1and a single normally closed contact P0813-3. The push buttons P0810 toP0813 are associated with the operation of a group of relays R11 to R14respectively which control the selection of the new settings of thefront saw blades and the cancellation of the previous settings in amanner similar to the rear saw blades. Consequently, the description ofthe operation of relays R11 to R14 will be omitted since it is identicalto the operation of relays R1 to R8 associated with the selection of thesettings of the rear saw blades. Relays R11 to R14 are also associatedwith pilot lights P11 to P14 which indicate the selection made.

Relays CR7 to CR10 in combination with limit switches L813 to L816determine the stopping position of the sliding bases moved by the motorM2 of the front unit. Relays CR7 to CR10 perform the same function asrelays CR1 to CR6 associated with the rear drive unit and act as memoryelements for determining the direction of rotation of the motor drivingthe front saw blades. Similarly, the limit switches L813 to L816 areoperated upon the passage'of the sliding bases at each position and aresubsequently released to the position illustrated in FIG. 8 afterpassage of the sliding bases.

Timing-relay T1 is connected across lines L3 to L4 and is operated uponclosure of switch (FIG. 7). T iming-relay T1 has normally closedcontacts Tl-l in the energization circuit of relay CR7. Shortly afterenergization of timing relay T1, contacts Tl-l are open but relay CR7has enough time to lock operated through its own contact CR7-l and limitswitch L812.

Let us assume now that the sliding base is moving from its minimumpresetting position P0810 to position P0812. The operation of pushbutton P0812 will operate relay R13 which will lock operated through itsown contact R13-1 and also close contact R13-2 to energize relay CR 0UTthrough limit switch L815 associated with position P0812 and throughnormally closed contacts CR9-2 and CR lN-l. The operation of relay CR0UT will close contact CR=0UT2 to operate relays R16 and M OUT. Theoperation of M OUT will close contact M 0UT-1 in the energizing circuitof motor M2. When the sliding bases, in moving from position P0810 toP0812, leave position P0810, relay CR7 is maintained energized throughits own contact CR7-1 and, when the sliding bases pass position P0811and reach position P0812, relays CR8 and CR9 are successively operatedby limit switches L814 and L815 and lock operated through theirowncontacts. It will be noted that the operation of relays CR7 to CR9open contacts CR7-2 to CR9-2 and close contacts CR7-3 to CR9-3. Theclosure of contacts CR7-3 to CR9-3 prepares a circuit for theenergization of relay CR,IN for returning the sliding bases to positionsP0810 or P081 1 if it is later on required. It is therefore seen thatrelays CR7 to CR10 act as memory elements for controlling the directionof movement of the sliding bases.

Assuming now that push button P0811 is pushed, relay R12 will beenergized and lock operated through its own contact R12-1. The operationof push button P0811 will open contacts P0811-2 and P0811-3 to releaserelay R13 previously operated. The operation of relay R12 will alsoclose contact R12-2 to energize relay CR IN through limit switch L814associated with position P0811 and now closed contacts CR7-3 and CR8-3.The operation of relay CR,IN will close contact CR IN-Z and energizerelay R15 and relay MJN. The energization of relay M IN closes contact MlN-l to cause the motor M2 to rotate in a direction opposite to theprevious direction to return the sliding bases to position. P0811. Uponarrival of the sliding bases at position P0811, limit switch L814 isoperated to release relay CR- IN and to stop the motor. As mentionedpreviously, relays R15 and R16 control the energization of brake windingPB2.

Limit switches L17 and L18 are positioned directly on the frame of thequadruple band saw and open the circuit of the motor M2 directly in caseof failure of the limit switches L813 to L816 when the sliding basesreach a maximum or a minimum setting position.

Limit switch L819 is a safety switch in the circuit of relay M OUT forstopping the motor M2 at the maximum setting position.

Relay R17 is energized by a push button EM-STOP which may be operated incase of an emergency to cause immediate stopping of the front and rearmotors. The energization of relay R17 opens contact R174 (FIG. 7) andR17-2 (FIG. 8) to deenergize relays R1 to R8, and R11 and R14. However,relays CR1 to CR which are energized directly from line L1 to L3 are notaffected by the operation of the emergency push button EM-STOP and thuskeep memorizing the position of the sliding bases.

Pilot light P15 is connected in series with normally closed contacts CRIN-3 and CR OUT-3 and is used to indicate that the sliding bases havereached the selected position.

Let us now consider the simultaneous operation of the two drive units 16and 18 when the setting of the rear saw blades is changed towards alower setting position and that it is desired to maintaina presetdistance between the front and rear saw blades. For example, let usassume that the front saw blades are positioned at position P0810corresponding to a predetermined distance between the front and rear sawblades and that it is required to maintain such position whatever may bethe displacement desired for the rear saw blades. As mentionedpreviously, upon displacement of the rear sliding bases following a newlower setting of the rear saw blades, the cams of the cam box will bedisplaced and, consequently, limit switch L813 associated with positionP0810 will be released. The release of limit switch L813 combined withthe energization of relay CR7 through limit switch L812, and with theenergization of relay R11 associated position P0810 will energize relayCR IN to cause the movement of the drive unit of the front sliding basesto follow the movement of the rear sliding bases. When the rear slidingbases reach their new position, the cam of the cam box 78 correspondingto position P0810 will operate limit switch L813 to release CR IN andthus stop the front drive unit. The relative setting between the frontand rear sliding bases is thus maintained.

It will be understood that the limit switch L812 is not associated withany of the positions of the from sliding bases. Such limit switch isused to determine the direction of movement of the front sliding baseswhen positioned at position P0810 upon setting of a higher position forthe rear sliding bases. When limit switch L8 12 is opened due to thedisplacement of the rear sliding bases outwardly and relay CR7 is thusreleased, relay CR OUT will be operated to cause the drive unit of thefront sliding bases to move the front saw blades outwardly.

Referring to FIGS. 10 and 11, each cam box 40 or 78 comprises a housing100 having a cover 102 secured thereto by locking devices 104. Withinhousing 100 is mounted for rotation a shaft 105 upon which are secured anumber of cams 106. Within the housing, there is provided a structure108 holding a transversal bar 110 upon which are mounted limit switchessuch as limit switches LS1 to L88 to L813 to L816 of FIGS. 7 and 8. Theswitches L81 to LS8 to L813 to'LSl6 of FIGS. 7 and 8. The shaft isthreaded and the angu- Iar position of the cams in front of the limitswitches is fixed by means of screws such as the one illustrated at 112in FIG. 11.

In order to permit easy adjustment of the length of the depression 114in the cams 106, each cam is made of two discs each having a depressiontherein, and the adjustment is made by means of a slot 116 in one discand a cap screw 119 threaded into a top hole in the other disc. Byadjusting the angular position of the two discs with respect to. eachother, the length of the depression 114 may be varied at will. It may benoted here that the angular position of the cams 106 on the shaft willdetermine the stopping position of the saw blades. In order to changethe angular position of the earns, the nuts 112 are loosened up and thetwo locked discs of the cam 106 are adjusted to their proper position.Once the cam is adjusted in position, screw 112 is tightened. It is tobe understood that each cam box contains a number of cams which isdependent upon the number of limit switches required, such number oflimit switches being itself dependent upon the desired number ofsettings of the quadruple band saw.

I claim 1. A system for controlling the setting of a quadruple band sawhaving a fixed frame, a pair of rear and a pair of front sliding basesslidably mounted on said fixed frame and respectively supporting a pairof saw blades, and a drive unit for operating each pair of sliding basesin synchronism, said system comprising:

a. a first device including means for controlling the drive unit of therear pair of sliding bases; and

b. a second device including means for controlling the drive unit of thefront pair of sliding bases to adjust the distance of the front pair ofsaw blades with respect to the rear pair of saw blades when the rearpair of saw blades is stationary and means responsive to movement ofsaid pair of rear sliding bases under the control of said first deviceto energize the front drive unit for maintaining a preset relativedistance between the front pair of saw blades and the rear pair of sawblades when the rear pair of saw blades is moving.

2. A system as defined in claim 1, wherein said means for controllingthe drive unit of the rear pair of sliding bases includes switchingmeans located in the energizing circuit of the rear drive unit andcorresponding to the number of preset positions of said rear pair of sawblades, and positioning means responsive to movement of said rearsliding bases a distance corresponding to a preset position foroperating a corresponding one of said switching means to deenergize therear drive unit.

3. A system as defined in claim 2, wherein the switching means are limitswitches and wherein said positioning means includes a first chainsprocket mounted for rotation on said frame, a cam box secured to saidfixed frame and having a main shaft carrying a number of cams foroperating said limit switches and a second chain sprocket secured to theend of said shaft, and a chain passing around said first and secondsprockets and having both ends thereof secured to said sliding baseswhereby energization of said rear drive unit will cause movement of saidchain and rotation of the cam box shaft until a limit switchcorresponding to a preset position is operated to deenergize said reardrive unit.

4. A system as defined in claim 1, wherein said means for controllingthe drive unit of the front pair of sliding bases includes switchingmeans positioned in the energizing circuit of the drive unit of thefront pair of saw blades and corresponding to the number of presetpositions of said front pair of saw blades, and positioning meansassociated with said front sliding bases and responsive to thedisplacement of the front sliding bases when the rear sliding bases arestationary for operating one of said switching means corresponding to apreset position of said front saw blades to deenergize the front driveunit when said preset position has been reached.

5. A system as defined in claim 4, wherein said switching means arelimit switches and wherein said positioning means includes two bracketsfastened to the fixed frame respectively at the rear and front sawsides, a shaft journalled in said brackets, first chain sprockets keyedone on each end of said shaft, second chain sprockets freely mounted oneon each bracket, a chain coupling the chain sprockets on the front sideof the quadruple band saw and having both ends thereof secured to saidfront sliding bases whereby movement of said front sliding bases willrotate said chain sprockets and the shaft coupled to said first chainsprockets, a cam box mounted on one of the rear sliding bases andincluding a main shaft carrying a number of cams operating said limitswitches, a third chain sprocket secured to the end of the cam boxshaft, and a second chain interconnecting the first chain sprocket onthe rear end of said shaft and said third chain sprocket, wherebydisplacement of the second chain due to the rotation of said firstmentioned shaft will cause rotation of the shaft of said cam box,whereas the displacement of the cam box due to the movement of the rearsliding bases when the front sliding bases are stationary willautomatically rotate the shaft of the cam box to displace the cams andenergize the front drive unit to follow the rear drive unit, thusmaintaining a relative distance between the rear and front pairs of sawblades.

6. A system as defined in claim 5, further comprising additional chainsprockets freely mounted on said sliding bases and coupled by saidsecond chain, said additional sprockets being positioned on either sideof said first mentioned shaft to compensate for the variations in thedistance between said first mentioned shaft and the shaft of the cam boxwhen the rear sliding bases are moved. 7 t

7. A system as defined in claim 1, further comprising a control circuitincluding position selection switches, selection relays responsive tothe operation of said selection switches, switching means located in theenergizing circuit of said drive units and operated by said first andsecond devices, and memory elements responsive to said selectionswitches and to said switching means for determining the direction ofmovement of said drive units and for ensuring stopping of the slidingbases at the selected positions.

8. A system as defined in claim 3, wherein each cam of said cam box ismade of two discs having a depression at the circumference thereof, saidtwo discs being placed in contact with each other and positioned in sucha way as to provide an overall depression which may be varied in lengthby relative rotation of one disc with res ect to the other.

9. A system as defined in claim 5, wherein each cam of said cam box ismade of two discs having a depression at the circumference thereof, andwherein said two discs are brought in contact with each other in such amanner as to provide an overall depression of variable length when thetwo discs are moved with respect to each other.

1. A system for controlling the setting of a quadruple band saw having afixed frame, a pair of rear and a pair of front sliding bases slidablymounted on said fixed frame and respectively supporting a pair of sawblades, and a drive unit for operating each pair of sliding bases insynchronism, said system comprising: a. a first device including meansfor controlling the drive unit of the rear pair of sliding bases; and b.a second device including means for controlling the drive unit of thefront pair of sliding bases to adjust the distance of the front pair ofsaw blades with respect to the rear pair of saw blades when the rearpair of saw blades is stationary and means responsive to movement ofsaid pair of rear sliding bases under the control of said first deviceto energize the front drive unit for maintaining a preset relativedistance between the front pair of saw blades and the rear pair of sawblades when the rear pair of saw blades is moving.
 1. A system forcontrolling the setting of a quadruple band saw having a fixed frame, apair of rear and a pair of front sliding bases slidably mounted on saidfixed frame and respectively supporting a pair of saw blades, and adrive unit for operating each pair of sliding bases in synchronism, saidsystem comprising: a. a first device including means for controlling thedrive unit of the rear pair of sliding bases; and b. a second deviceincluding means for controlling the drive unit of the front pair ofsliding bases to adjust the distance of the front pair of saw bladeswith respect to the rear pair of saw blades when the rear pair of sawblades is stationary and means responsive to movement of said pair ofrear sliding bases under the control of said first device to energizethe front drive unit for maintaining a preset relative distance betweenthe front pair of saw blades and the rear pair of saw blades when therear pair of saw blades is moving.
 2. A system as defined in claim 1,wherein said means for controlling the drive unit of the rear pair ofsliding bases includes switching means located in the energizing circuitof the rear drive unit and corresponding to the number of presetpositions of said rear pair of saw blades, and positioning meansresponsive to movement of said rear sliding bases a distancecorresponding to a preset position for operating a corresponding one ofsaid switching means to deenergize the rear drive unit.
 3. A system asdefined in claim 2, wherein the switching means are limit switches andwherein said positioning means includes a first chain sprocket mountedfor rotation on said frame, a cam box secured to said fixed frame andhaving a main shaft carrying a number of cams for operating said limitswitches and a second chain sprocket secured to the end of said shaft,and a chain passing around said first and second sprockets and havingboth ends thereof secured to said sliding bases whereby energization ofsaid rear drive unit will cause movement of said chain And rotation ofthe cam box shaft until a limit switch corresponding to a presetposition is operated to deenergize said rear drive unit.
 4. A system asdefined in claim 1, wherein said means for controlling the drive unit ofthe front pair of sliding bases includes switching means positioned inthe energizing circuit of the drive unit of the front pair of saw bladesand corresponding to the number of preset positions of said front pairof saw blades, and positioning means associated with said front slidingbases and responsive to the displacement of the front sliding bases whenthe rear sliding bases are stationary for operating one of saidswitching means corresponding to a preset position of said front sawblades to deenergize the front drive unit when said preset position hasbeen reached.
 5. A system as defined in claim 4, wherein said switchingmeans are limit switches and wherein said positioning means includes twobrackets fastened to the fixed frame respectively at the rear and frontsaw sides, a shaft journalled in said brackets, first chain sprocketskeyed one on each end of said shaft, second chain sprockets freelymounted one on each bracket, a chain coupling the chain sprockets on thefront side of the quadruple band saw and having both ends thereofsecured to said front sliding bases whereby movement of said frontsliding bases will rotate said chain sprockets and the shaft coupled tosaid first chain sprockets, a cam box mounted on one of the rear slidingbases and including a main shaft carrying a number of cams operatingsaid limit switches, a third chain sprocket secured to the end of thecam box shaft, and a second chain interconnecting the first chainsprocket on the rear end of said shaft and said third chain sprocket,whereby displacement of the second chain due to the rotation of saidfirst mentioned shaft will cause rotation of the shaft of said cam box,whereas the displacement of the cam box due to the movement of the rearsliding bases when the front sliding bases are stationary willautomatically rotate the shaft of the cam box to displace the cams andenergize the front drive unit to follow the rear drive unit, thusmaintaining a relative distance between the rear and front pairs of sawblades.
 6. A system as defined in claim 5, further comprising additionalchain sprockets freely mounted on said sliding bases and coupled by saidsecond chain, said additional sprockets being positioned on either sideof said first mentioned shaft to compensate for the variations in thedistance between said first mentioned shaft and the shaft of the cam boxwhen the rear sliding bases are moved.
 7. A system as defined in claim1, further comprising a control circuit including position selectionswitches, selection relays responsive to the operation of said selectionswitches, switching means located in the energizing circuit of saiddrive units and operated by said first and second devices, and memoryelements responsive to said selection switches and to said switchingmeans for determining the direction of movement of said drive units andfor ensuring stopping of the sliding bases at the selected positions. 8.A system as defined in claim 3, wherein each cam of said cam box is madeof two discs having a depression at the circumference thereof, said twodiscs being placed in contact with each other and positioned in such away as to provide an overall depression which may be varied in length byrelative rotation of one disc with respect to the other.